Characterization of telomere DNA among five species of pteridophytes and bryophytes

Abstract

Higher plant chromosomes possess tandem repeats of TTTAGGG as telomere DNA, while the alga Chlamydomonas reinhardtii contains tandem repeats of TTTTAGGG as telomere DNA. This study analysed the telomere composition in five species of mosses and ferns. Genomic Southern hybridization against a tobacco telomere probe indicated intense and highly diffuse signals in all three pteridophytes and the two bryophytes used here. DNAs from a moss Barbula unguiculata, a liverwort Marchantia paleacea var. diptera and a fern Psilotum nudum were examined further by kinetic DNA digestion by nuclease Bal31 followed by hybridization to the tobacco telomere probe. All three plants gave signals hypersensitive to the nuclease treatment confirming the telomeric location of the hybridization signals. The average size of the telomere repeat was 0.5 kbp in the liverwort. The liverwort telomeric fragments were cloned in a plasmid vector. Sequencing of the cloned DNA showed that the terminal sequences are composed of tandem repeats of TTTAGGG and the orientation of the repeats is the same as that in higher plants. Based on these results, it was concluded that both the pteridophytes and the bryophytes have the higher-plant-type telomere sequences.

Keywords:

• FERN
• LIVERWORT
• MOSS
• PLANT GENOME
• TELOMERE REPEAT SEQUENCE
• CHROMOSOME END